1. Field of the Invention
The present invention relates generally to wheelchairs and more particularly to an anti-rollback assembly that operatively associates with a wheelchair to prevent the wheelchair from rolling backwards and away from its occupant as the occupant attempts to mount or dismount the wheelchair, yet permits the wheelchair in an unoccupied state to be moved in a forward direction.
The anti-rollback assembly of the present invention is especially suitable for wheelchairs of invalids, the cognitively impaired, the elderly, and sufferers of physically and mentally disabling diseases such as Alzheimer's.
2. Description of the Related Art
Almost all wheelchairs possess a parking brake in one form or another which, when actuated, maintains the wheelchair in a stationary position by preventing one or both of the large drive wheels of the wheelchair from rotating about a common central axis. Perhaps the most crucial periods for the wheelchair to remain stationary are when a person attempts to sit down in and occupy the wheelchair and when the occupant attempts to stand up from and vacate the wheelchair. The natural motion of a person performing these acts imparts a force in the rearward direction on the wheelchair, which, without the benefit of an actuated parking brake, causes the wheelchair to move backwards and away from the person.
As a consequence of the mental and physical infirmities suffered by many wheelchair occupants, especially patients suffering from Alzheimer's disease and other mental frailties, occupants often forget to actuate manually-operated parking brakes prior to attempting to rise from the wheelchair, or neglect to inspect the parking brake to ensure it is engaged in a locked position prior to attempting to sit down into the wheelchair. Failure to engage the manually-operated parking brake in its locked position presents a serious hazard of injury to both the occupant and his or her caretaker, since the wheelchair is unimpeded from rolling back and away from the occupant as the occupant attempts to rise from or sit down in the wheelchair.
To address the shortcomings of manually-operated parking brakes, several different automatically-operated locking brake assemblies have been proposed. U.S. Pat. No. 5,203,433 sets forth a discussion of some conventional automatic locking brake assemblies. Each of the conventional assemblies mentioned in U.S. Pat. No. 5,203,433 is characterized by the provision of a locking member that, unless manually disengaged, prevents or at least substantially obstructs both the forward or rearward movement of the wheelchair with which the assembly is associated when the wheelchair is unoccupied.
However, one of the most important functions served by an automatic wheelchair brake is that it not only prevent the wheelchair from rolling backwards and away from its occupant as the occupant mounts or dismounts the wheelchair, but that the brake also not substantially obstruct the forward motion of the wheelchair when unoccupied so that the unoccupied wheelchair can be easily maneuvered to a desirable location for use or temporary storage.
A long-felt need therefore exists to provide an automatically-operated anti-rollback assembly for a wheelchair that biases a braking mechanism into an activated position when the wheelchair is unoccupied to prevent the wheelchair from rolling back when it is mounted or dismounted in normal operation, yet, while in the activated position, permits the forward motion of the unoccupied wheelchair.